1. Field of the Invention
The present invention relates to a system for bleaching discolored teeth, used for bleaching pigments (coloration, discoloration) deposited on teeth, and more particularly, it relates to a system for bleaching discolored teeth, having a function of irradiating with light for bleaching teeth by a photocatalytic action, wherein a chemical agent comprising titanium dioxide and aqueous hydrogen peroxide is applied to the surface of the teeth and these are irradiated with the light.
2. Description of the Related Art
In recent years, in dental therapy, demands for so-called cosmetic improvements, in which the contour, alignment and integrity etc of the teeth are improved are increasing. Of these, recently, cases in which young women are seeking dental therapy with a view to whitening the teeth, as an important element in facial beauty, are increasing. Causes of dental discoloration or pigmentation/staining may be generally divided into so-called extrinsic causes such as for example deposition of colored substances (tobacco, tea stains and the like), pigment-generating bacteria, discoloration of repair materials (chiefly composite resin), or metallic salts (chiefly amalgam, silver nitrate, or ammonia silver) and so-called intrinsic causes such as for example aging, chemical substances or chemical agents (fluorine, tetracycline and the like), dysmetabolism or hereditary diseases, or dental injuries; however, in dental health therapy, the chief applications of the bleaching method are in the latter i.e. intrinsic cases, where there is dental discoloration of pulpless teeth.
Several methods have been proposed in the past as methods for the cosmetic improvement of discolored teeth, among which bleaching may be considered a highly effective method for the preservation of dentine, despite drawbacks such as occasional recurrence, when methods suited to individual cases are selected and properly carried out.
Bleaching is essentially a method for decolorizing colored substances by means of a chemical reaction. In the past there have been various reports of bleaching agents comprising a variety of chemical agents based on vital bleaches and non-vital bleaches, as well as bleaching methods involving the use of such agents.
The following are some typical examples.
1) Methods of bleaching using 30% H2O2 as the chemical agent, with combined use of light and heat on the aqueous hydrogen peroxide.
2) Bleaching using 30% H2O2 as the chemical agent, and the concurrent use of high frequency current on the aqueous hydrogen peroxide.
3) Bleaching in which a paste comprising Aerosil (silica fine powder) mixed with 35% H2O2 is used as the chemical agent, and the aqueous hydrogen peroxide and Aerosil paste is applied.
4) Bleaching in which a paste obtained by kneading a 35% H2O2 solution and a powder (ingredients comprising potassium sulfate, manganese sulfate, silicon dioxide, or the like) is used as the chemical agent (MATSUKAZE HIGHLIGHT, Trademark).
5) Bleaching in which a mixture of 1 mL of 30% HCl, 1 mL of 30% H2O2, and 0.2 mL of diethyl ether is used as the chemical agent (improved MacInnes bleaching).
6) A method in which a kneaded paste of 30% H2O2 and a sodium perborate powder is used as the chemical agent (working bleach method).
Many other bleaching methods have also been reported, such as the dental bleaching agent and method comprising a mixture of aqueous hydrogen peroxide and ortho-phosphoric acid (Japanese Laid-Open Patent Publication No. H8-143436/1996), the bleaching agent comprising a mixture of silicic anhydride with aqueous hydrogen peroxide, and the vital bleaching method comprising the application of such a bleaching agent (Japanese Laid-Open Patent Publication No. H5-320033/1993), and the dental bleaching composition comprising a dental bleaching agent (such as hydrogen-urea peroxide, hydrogen peroxide-carbamide, and carbamide peroxide) and a matrix material (such as carboxymethylene), a method for bleaching teeth using the above (Japanese Laid-Open Patent Publication No. H8-113520/1996) and a method for bleaching discolored teeth using photocatalysis of titanium dioxide (published Japanese Patent No. 3030380/2000).
As can be seen from the foregoing prior art, a technique is known to perform bleaching of pigment deposited on teeth (coloration, discoloration) by combining irradiation with light with a chemical agent based on titanium dioxide and aqueous hydrogen peroxide. For example, in the above Japanese Patent publication No. 3030380, regarding the irradiation with light, it is merely stated that, although it is desirable to perform the irradiation with high-energy ultraviolet light, from the point of view of generating activated oxygen by the photocatalytic effect and from the point of view of its oxidative action, since ultraviolet light affects the human body, it is desirable to perform irradiation with violet light. However, what kind of light is actually effective is not known, and the details thereof are not known.
Also, the bleaching function changes considerably depending on the concentration of the aqueous hydrogen peroxide. When aqueous hydrogen peroxide is introduced into the mouth, in the case of aqueous hydrogen peroxide of high concentration, there is an adverse effect on the human body and in recent years, in accordance with various tests, from the point of view of both bleaching and safety, the concentration of aqueous hydrogen peroxide is determined as 3%.
However, the optimum conditions for light and chemical agents including 3% aqueous hydrogen peroxide have not been discovered; for example, even if a specific type of light has a bleaching function, heat is also generated by irradiation with light, so that the tooth crown is heated whilst bleaching, causing inflammation of the pulp; or there was the problem of emission of ultraviolet light, which has an adverse effect on the human body.
The present invention has been made in view of the above, its object is to provide a system for bleaching discolored teeth, wherein, when bleaching teeth using a chemical agent comprising titanium dioxide and aqueous hydrogen peroxide, reliable bleaching of the teeth can be achieved, yet little heat is applied to the teeth and essentially no ultraviolet light that has an adverse effect on the human body is irradiated.
Briefly, this object and other objects of the present invention as hereinafter will become more readily apparent can be attained by an apparatus for bleaching discolored teeth, which comprises:
a light source, a mirror for condensing the light from said light source, a wavelength cut-off filter and a light-emitting section, wherein the light emitted from the light-emitting section having a wavelength of 800 nm or higher is cut from the spectrum of light emitted by the light-emitting section by the wavelength cut-off filter, the radiant energy of light of the wavelength range of 380 to 420 nm is at least 37 mW/cm2, and the ratio of light of the wavelength range of 380 to 420 nm to light of the wavelength range of 200 to 800 nm is at least 36% of the light emitted from the light-emitting section.